Eight iron age (from 500 BC to 1200 AD in Finland) graves in Käräjämäki, Eura, Finland. The graves were originally small mounds that contained wooden coffin. The holes formed when the coffins decayed. The whole site contains 169 graves and a [stone circle](https://en.wikipedia.org/wiki/Stone_circle_(Iron_Age)).
More info:
* [Location in Google Maps](https://goo.gl/maps/nwCRx8G81rGYnrCE9)
* [Wikipedia (only in finnish)](https://fi.wikipedia.org/wiki/K%C3%A4r%C3%A4j%C3%A4m%C3%A4ki_(Eura))
* [Finnish Heritage Agency site info (only in finnish)](https://www.kyppi.fi/to.aspx?id=112.50010027)